AU2022219430A1 - Device and method for liquefying a fluid such as hydrogen and/or helium - Google Patents

Abstract

Disclosed is a device for liquefying a fluid, comprising a circuit (3) for fluid to be cooled, the device (1) comprising a set of one or more heat exchangers (6, 7, 8, 9, 10, 11, 12, 13) exchanging heat with the circuit (3) of fluid to be cooled, at least one first cooling system (20) exchanging heat with at least some of the set of one or more heat exchangers (6, 7, 8, 9, 10, 11, 12, 13), the first cooling system (20) being a refrigerator with refrigeration cycle of a cycle gas mostly comprising helium, the refrigerator (20) comprising, arranged in series in a cycle circuit (14): a cycle gas compression mechanism (15), at least one cycle gas cooling member (16, 5, 6, 8, 10, 12), a mechanism (17) for expansion of the cycle gas and at least one expanded cycle gas heating member (13, 12, 11, 10, 9, 8, 7, 6, 5), wherein the compression mechanism comprises at least four compression stages (15) in series, consisting of a set of one or more centrifuge-type compressors (15), the compression stages (15) being mounted on shafts (19, 190) rotated by a set of one or more motors (18), the expansion mechanism comprising at least three expansion stages in series, consisting of a set of centripetal turbines (17), the at least one cycle gas cooling member (16, 5, 6, 8, 10, 12) being configured to cool the cycle gas at the outlet of at least one of the turbines (17) and wherein at least one of the turbines (17) is coupled to the same shaft (19) as at least one compression stage (15) so as to supply the compression stage (15) with the mechanical work produced during the expansion.

Description

Device and method for liquefying a fluid such as hydrogen and/or helium The invention relates to a device and a process for liquefying

a fluid such as hydrogen and/or helium.

The invention relates more particularly to a device for

refrigerating and/or liquefying a fluid such as hydrogen and/or

helium, comprising a circuit for fluid to be cooled having an

upstream end intended to be connected to a source of fluid and

a downstream end intended to be connected to a member for

collecting the fluid, the device comprising a set of heat

exchanger(s) in heat exchange with the circuit for fluid to be

cooled, the device comprising at least a first cooling system in

heat exchange with at least part of the set of heat exchanger(s),

the first cooling system being a refrigerator that performs a

refrigeration cycle on a cycle gas, said refrigerator comprising

the following, disposed in series in a cycle circuit: a mechanism

for compressing the cycle gas, at least one member for cooling

the cycle gas, a mechanism for expanding the cycle gas and at

least one member for heating the expanded cycle gas, wherein the

compression mechanism comprises a plurality of compression

stages in series that are composed of a set of centrifugal

impeller compressor(s), the compression stages being mounted on

shafts that are driven in rotation by a set of motor(s), the

expansion mechanism comprising at least one expansion stage

composed of a set of centripetal turbine(s) having a determined

working pressure at the inlet, and wherein the turbine, or

respectively at least one of the turbines, is coupled to the

same shaft as at least one compression stage so as to provide

the mechanical work produced during the expansion to the

compression stage.

The prior-art solutions for liquefying hydrogen (H2) incorporate

cycle compressors which obtain relatively low isothermal

efficiencies (of about 60% to 65%) and have a relatively limited volumetric capacity at the cost, however, of quite considerable investment and high maintenance costs.

Document EP3368630 Al describes a known process for liquefying

hydrogen.

An aim of the present invention is to overcome all or some of

the drawbacks of the prior art outlined above.

To that end, the device according to the invention, which is

otherwise in accordance with the generic definition thereof

given in the above preamble, is essentially characterized in

that the at least one turbine and the corresponding compression

stage that are coupled are structurally configured such that the

pressure of the cycle gas exiting the turbine differs by no more

than 40% and preferably by no more than 30% or by no more than

20% from the pressure of the cycle gas at the inlet of the

compression stage, and/or the at least one turbine and the

corresponding compression stage that are coupled are

structurally configured such that the pressure of the cycle gas

entering the turbine differs by no more than 40% and preferably

by no more than 30% or by no more than 20% from the pressure of

the cycle gas at the outlet of the compression stage.

Furthermore, embodiments of the invention may comprise one or

more of the following features:

- the expansion mechanism comprises at least two expansion

stages in series that are composed of a set of centripetal

turbines in series, and in that, in the direction of circulation

of the cycle gas, at least two turbines in series are coupled

respectively to compression stages considered in the reverse

order of their disposition in series, that is to say that at

least one turbine is coupled to a compression stage situated

upstream of a compression stage coupled to another turbine which

precedes it in the cycle circuit,

- the expansion rate across the at least one turbine coupled

to a compression stage is configured to produce a drop in

pressure of the cycle gas of the the value differs by no more than 40% from the value of the increase in pressure across the compression stage to which said turbine is coupled,

- the compression mechanism comprises solely centrifugal

compressors,

- the expansion mechanism comprises solely centripetal

turbines,

- the device comprises n turbines and k compressors, n and k

being integers such that k k n,

- the mechanical coupling of the at least one turbine and of

the compression stage or stages to one and the same shaft is

configured to ensure an identical or substantially identical

rotational speed of the turbine and of the compression stages

that are coupled,

- the device comprises sixteen compression stages and eight

turbines, or twelve compression stages and six turbines, or eight

compression stages and four turbines, or six compression stages

and three turbines, or four compression stages and three

turbines, or three compression stages and two or three turbines,

or two compression stages and one or two turbines,

- the set of heat exchanger(s) comprises at least one heat

exchanger in which two separate portions of the cycle circuit

under separate thermodynamic conditions perform circulation

simultaneously in countercurrent operation for the cooling and

the heating of the cycle gas, respectively.

The invention also relates to a process for producing hydrogen

at cryogenic temperature, notably liquefied hydrogen, using a

device according to any one of the features above or below,

wherein the pressure of the cycle gas at the inlet of the

mechanism for compressing the cycle gas lies between two and

forty bar abs and notably lies between eight and thirty five bar

abs.

According to other possibilities, the cycle gas comprises at

least one of the following: helium, hydrogen, nitrogen, neon,

freon, a hydrocarbon (to be completed), and/or the at least one member for cooling the cycle gas is configured to cool the cycle gas at the outlet of the at least one turbine or at the outlet of at least one of the turbines.

The invention may also relate to any alternative device or

process comprising any combination of the features above or below

within the scope of the claims.

Further particular features and advantages will become apparent

from reading the following description, which is given with

reference to the figures, in which:

[fig. 1] shows a schematic and partial view illustrating the

structure and the operation of a first possible exemplary

embodiment of the invention,

[fig. 2] shows a schematic and partial view illustrating the

structure and the operation of a second possible exemplary

embodiment of the invention,

[fig. 3] shows a schematic and partial view illustrating the

structure and the operation of a third possible exemplary

embodiment of the invention,

[fig. 4] shows a schematic and partial view illustrating the

structure and the operation of a fourth possible exemplary

embodiment of the invention,

[fig. 5] shows a schematic and partial view illustrating the

structure and the operation of a fifth possible exemplary

embodiment of the invention,

[fig. 6] shows a schematic and partial view illustrating a detail

of the fourth possible exemplary embodiment of the invention,

illustrating a possible example of the structure and operation

of a motor-turbocompressor of the device ?

[fig. 7] shows a schematic and partial view illustrating an

example of a coupled turbine and compressor wheel with the

respective inlet and outlet pressures,

[fig. 8] shows a schematic and partial view illustrating another

simplified embodiment.

The device 1 for liquefying a fluid shown in [fig. 1] may be

intended for the liquefaction of hydrogen but can also be applied

to other gases, notably helium or any mixture. Equally, the

device may ensure the cooling or the liquefaction of any other

fluid: natural gas, helium, methane, biomethane, nitrogen,

oxygen, neon, combination of these gases. The device 1 comprises

a circuit 3 for fluid to be cooled (typically hydrogen) having

an upstream end intended to be connected to a source 2 of gaseous

fluid and a downstream end 23 intended to be connected to a

member 4 for collecting the liquefied fluid. The source 2 may

comprise typically an electrolyzer, a hydrogen distribution

network, a steam methane reforming (SMR) unit or any other

suitable source(s).

The device 1 comprises a set of heat exchangers 6, 7, 8, 9, 10,

11, 12, 13 disposed in series in heat exchange with the circuit

3 for fluid to be cooled. A single heat exchanger is also

conceivable.

The device 1 comprises at least a first cooling system 20 in

heat exchange with at least part of the set of heat exchangers

5, 6, 7, 8, 9, 10, 11, 12, 13.

This first cooling system 20 is a refrigerator that performs a

refrigeration cycle on a cycle gas.

This cycle gas comprises, for example, at least one of the

following: helium, hydrogen, nitrogen, neon, freon, a

hydrocarbon.

This refrigerator 20 comprising the following, disposed in

series in a cycle circuit 14 (preferably closed in the form of

a loop): a mechanism 15 for compressing the cycle gas, at least

one member 16, 5, 6, 8, 10, 12 for cooling the cycle gas, a

mechanism 17 for expanding the cycle gas and at least one member

13, 12, 11, 10, 9, 8, 7, 6, 5 for heating the expanded cycle

gas.

As illustrated, the set of heat exchanger(s) which cools the

hydrogen to be liquefied preferably comprises one or a plurality of countercurrent heat exchangers 5, 6, 8, 10, 12 which are disposed in series and in which two separate portions of the cycle circuit 14 perform circulation simultaneously in countercurrent operation (respectively for the cooling and the heating of separate flows of the cycle gas).

That is to say that this plurality of countercurrent heat

exchangers forms both a member for cooling the cycle gas (after

the compression and after expansion stages, for example) and a

member for heating the cycle gas (after the expansion and before

the return to the compression mechanism).

The compression mechanism comprises at least two compression

stages 15 composed of a set of centrifugal compressors that are

disposed in series (and possibly in parallel).

A compression stage 15 may be composed of a wheel of a motorized

centrifugal compressor.

The compression stages 15 (that is to say the compressor wheels)

are mounted on shafts 19, 190 that are driven in rotation by a

set of motor(s) 18 (at least one motor). Preferably, all the

compressors 15 are of the centrifugal type.

For its part, the expansion mechanism comprises at least one

expansion stage formed of centripetal turbine(s) 17 (disposed at

least partially in series if there are a plurality of expansion

stages. Preferably, all the turbines 17 are of the centripetal

type and are mainly disposed in series).

At least one of the turbines 17 is coupled to the same shaft 19

as a compression stage 15 of a compressor so as to provide the

mechanical work produced during the expansion to the compressor.

The at least one turbine 17 and the corresponding compression

stage that are coupled are structurally configured such that the

pressure P2t of the cycle gas exiting the turbine 17 differs by

no more than 40% and preferably by no more than 30% or by no

more than 20% from the pressure Plc of the cycle gas at the inlet

of the compression stage 15 (cf. [fig. 7]).

Equally, the at least one turbine 17 and the corresponding

compression stage that are coupled are preferably also (or

possibly alternatively) structurally configured such that the

pressure of the cycle gas entering the turbine 17 differs by no

more than 40% and preferably by no more than 30% or by no more

than 20% from the pressure of the cycle gas at the outlet of the

compression stage.

This combination of particular technical features (centrifugal

compression, centripetal expansion, transfer of work from the

turbines to the compressors and regulation of the pressures

between the coupled compression and expansion wheels) improves

the efficiency of the device with respect to the known solutions.

This structural configuration of the turbines (for example

turbine wheel) and compression stages (for example compression

wheel) means that these two elements are dimensioned (shape

and/or dimension of the wheel and/or of their volute and/or of

their inlet distributor, if appropriate) to respectively perform

compressions and expansions of the same or similar absolute

values as specified above. That is to say that, by design, these

two coupled elements could reach these compression and expansion

ratios (without using another active or passive element in the

cycle circuit), preferably irrespective of the conditions of the

flow of cycle gas.

For example, the expansion rate across the at least one turbine

17 coupled to a compression stage may be configured to produce

a drop in pressure of the cycle gas, the value of which differs

by no more than 40% or by no more than 20% from the value of the

increase in pressure across the compression stage 15 to which

said turbine is coupled.

Referring for example to [fig. 7], if the compressor 15 is

coupled to the turbine 17 and operates between 10 bar and 15 bar

(compression of the flow initially at Plc = 10 bar to an outlet

pressure P2c = 15 bar), it is advantageous for the turbine 17 to cause this flow to expand to pressures of between 15 and 10 bar

(Plt = 15 bar and P2t = 10 bar).

This improves the distribution and balancing of the axial forces

of the shaft 19 which bears them.

Since the signs of the forces generated by the differences in

pressure across the wheels 15, 17 are opposite, this tends to

reduce the resultant of the axial forces.

This preferably also applies in the case of a plurality of

turbines in series coupled to one or more compressors 15.

Thus, as illustrated, the expansion mechanism may comprise at

least two expansion stages in series that are composed of a set

of centripetal turbines 17 in series.

In addition, in the direction of circulation of the cycle gas,

at least two turbines 17 in series are preferably coupled

respectively to compression stages 15 considered in the reverse

order of their disposition in series. That is to say that at

least one turbine 17 is coupled to a compression stage 15

situated upstream of a compression stage 15 coupled to another

turbine 17 which precedes it in the cycle circuit 14.

Preferably, the device comprises n turbines (expansion wheels or

stages) and k compressor wheels or stages, where k >= n. The

expansion rate selected across each turbine 17 is thus preferably

imposed as a function of the compressor to which they are coupled

(as explained above).

The device 1 may comprise one or more motor-turbocompressors in

part of the compression station. A motor-turbocompressor is an

assembly comprising a motor, the shaft of which directly drives

a set of compression stage(s) (wheel(s)) and a set of expansion

stage(s) (turbine(s)). This makes use of the mechanical

expansion work directly at one or more compressors of the cycle

gas.

The at least one member 16, 5, 6, 8, 10, 12 for cooling the cycle

gas may possibly be configured to cool the cycle gas at the

outlet of at least one of the turbines 17. That is to say that, after expansion in a turbine 17, the cycle gas may be cooled by a value typically lying between 2 K and 30 K.

For example, and as illustrated, the device 1 comprises more

compression stages 15 than turbines 17, for example twice as

many or approximately twice as many. Each turbine 17 may be

coupled to the same shaft 19 as a single respective compressor

wheel 15 that is driven by a respective motor 18. It is possible

for the other compressor wheel or wheels 15 (stage(s)) that are

not coupled to a turbine 17 to be mounted only on rotary shafts

190 driven by separate respective motors 18 (motor-compressor).

As illustrated, the compression stages 15 that are coupled to a

turbine 17 and the compressors that are not coupled to a turbine

17 may alternate in series in the cycle circuit 14.

The compression mechanism may comprise more than six compression

stages in series. Of course, this is in no way limiting. The

minimum compression rate (by the centrifugal technology) for

achieving the liquefaction of hydrogen should preferably be

about 1.3 to 1.6.

Four compression stages 15 in series make it possible notably to

obtain very good isothermal efficiency with respect to the known

solutions of piston compression, at the cost of a relatively

significant mass flow rate of helium.

In the non-limiting example illustrated in [fig. 1], only four

compression stages 15 and three turbines 17 are shown, but the

device 1 could comprise eight compression stages 15 and four

turbines 17. Any other distribution may be envisioned, for

example sixteen compression stages 15 and eight turbines 17, or

twelve compression stages and six turbines, or six compression

stages and three turbines, or four compressors and three

turbines, or three compression stages and two turbines

(expansion stages), or two compression stages and one expansion

stage, etc.

Cooling may be provided downstream of all or some of the

compression stages or downstream of all or some of the compressors 15 (for example via a heat exchanger 16 cooled by a heat transfer fluid or any other refrigerant that is notably different from the cycle gas). This cooling may be provided after each compression stage or, as illustrated, every two compression stages 15 (or more) or solely downstream of the compression station. Surprisingly, this distribution of the cooling not at the outlet of each of the compression stages 15 in series but every two (or three) compression stages 15 makes it possible to obtain cooling performance while limiting the costs of the device

1.

Equally, the at least one member for cooling the cycle gas may

optionally comprise a system 8, 10, 12 for cooling the cycle

gas, such as a heat exchanger, disposed at the outlet of at least

some of the turbines 17 in series.

This intermediate inter-expansion cooling makes it possible to

limit the value of the high pressure necessary to reach the

coldest temperatures of the cycle gas.

As illustrated in [fig. 1], the device 1 may comprise a system

for cooling the cycle gas, such as a heat exchanger, at the

outlet of all of the turbines 17 except for the last turbine 17

in series in the direction of circulation of the cycle gas. As

illustrated, this cooling system may be provided by the

aforementioned respective countercurrent heat exchangers 8, 10,

12.

This cooling after expansion enables temperature staging (that

is to say makes it possible to reach different, increasingly

lower temperatures after each expansion stage) to extract cold

for the fluid to be cooled. This temperature staging is obtained

by this arrangement and via a minimum compression rate obtained

for supplying these different turbines 17.

The arrangement of a plurality of centrifugal compression stages

15 in series upstream makes it possible to obtain this pressure

differential which enables sufficient staging of the cooling

downstream. Specifically, for the same pressure difference, the more the temperature decreases, the more the enthalpy drop with constant entropy during the expansion decreases. The effect of the arrangement of the turbines 17 in series and the cooling 8,

10 at the outlet of the turbines is to increase the mean mass

flow rate in the turbines 17 with respect to conventionally known

staging. The theoretical isentropic efficiency thus tends to

increase and therefore makes it possible to obtain better

efficiencies of the turbines 17.

In particular, the cooling 8, 10 between the expansion stages

allows the cycle fluid to reach the target liquefaction

temperatures without requiring an even greater overall

compression rate. The expansions are preferably isentropic or

quasi-isentropic. That is to say that the cycle fluid is cooled

progressively and the fluid liquefied.

Thus, the minimum temperature is reached directly at the outlet

of the last quasi-isentropic expansion stage (that is to say

downstream of the last expansion turbine 17). It is thus not

necessary to additionally provide an expansion valve of the

Joule-Thomson type downstream, for example. The cold and notably

a supercooling temperature of the hydrogen to be liquefied can

be obtained exclusively with the turbines 17 (extraction of

work).

Preferably, most or all of the turbines 17 are coupled to one or

more respective compressors 15.

As mentioned above, the successive turbines 17 are preferably

coupled respectively to compression stages 15 of compressors

considered in the reverse order of their disposition in series.

That is to say that, for example, a turbine 17 is coupled to a

compressor 15 situated upstream of a compressor 15 coupled to

the turbine 17 which precedes it.

The order of combination of the turbines 17 and compressors that

are coupled is therefore preferably at least partially reversed

between the turbines and the compressors (in the cycle circuit, a turbine that is further upstream is coupled to a compressor that is further downstream).

Thus, in the case for example of an architecture with six

compression stages 15 in series and three expansion stages in

series, the first turbine 17 (that is to say the first turbine

17 after the compression mechanism) may be coupled to the fifth

compressor 15 in series (fifth compression stage), while the

second turbine 17 may be coupled to the third compressor 15 in

series (third compression stage), the third turbine 17 may be

connected to the first compressor 15 in series (first compression

stage). It is possible for the other compressors 15 forming the

other compression stages to not be coupled to a turbine (motor

compressor system and not motor-turbocompressors). Thus, the

most powerful turbine 17 (the one furthest downstream) may be

coupled to the first compression stage (the first compression

stage intakes at the low pressure of the cycle). At this

relatively low pressure level, the greater the compression rate

of the compressor 15, the less the impact of the pressure drops

at its level is felt (and so on with the other compressors 15).

This example above is, of course, in no way limiting. For

example, the turbines 17 could be coupled respectively to the

even-numbered compressors 15 (the first turbine to the sixth

compressor, the second turbine to the fourth compressor, etc.)

or to the compressors directly in series (for example the first

turbine 17 to the sixth compressor 15, the second turbine to the

fifth compressor, etc.).

In the example illustrated with alternation of a compressor 15

that is coupled to a turbine 17 and then a compressor 15 that is

not coupled to a turbine, the working pressures of the turbines

17 may be set to the working pressures of the compressors 15 "one by one" or "two by two" (that is to say that the first

turbine 17 works at the compression rate of the 5th or 6th

compressors 15; equally, the second turbine 17 works at the

compression rate of the 3rd or 4th compressors, etc.). If consideration is given to a pair of two compressors 15 in series

(a compressor with a compression wheel that is coupled to a

turbine followed by a compressor with a compressor wheel that is

not coupled to a turbine), the first of these two compressors

compresses for example the cycle gas to a first pressure PA while

the second then compresses this cycle gas to a second pressure

PB, where PB > PA. The turbine 17 which will be coupled to the

first of these two compressors will preferably expand the cycle

gas from the second pressure PB to the first pressure PA. This

can be obtained, for example, by adjusting the characteristics

of this turbine 17 in accordance with this constraint. For

example, there is adjustment of the cross section of the

distributor calibrating the flow rate arriving at the turbine

17, this having an effect on the resulting pressure drop in the

distributor part and the turbine wheel part.

Thus, for example when turbines are coupled every two compression

stages in series, the pressure relationships described in detail

above (inlet/outlet) between the expansion and compression

stages that are coupled can therefore be applied either solely

to the compression stage that bears the turbine or to a set of

two compressor wheels in series. In addition, the mechanical

coupling or couplings of the turbines 17 and compressor wheels

15 to the same shaft 19 is (are) configured to ensure preferably

an identical (or substantially identical) rotational speed of

the turbine 17 and of the compressor wheels 15 that are coupled.

This makes it possible to make direct and effective use of the

expansion work in the device. If appropriate, the rotational

speeds of all the compressor and turbine wheels may be equal to

one and the same determined value.

A control member may optionally be provided for all or some of

the compression stages. For example, a variable-frequency drive

("VFD") may be provided for each motor 18 driving at least one

compression stage. This makes it possible to independently

adjust the speeds of a plurality of compression stages or each compression stage and thus the expansion without using a complex system of gears or a drive and a specific control means linked to variable vanes upstream of one or more compression stages.

This speed controlling member may be provided for the set of

compressors or for each compression stage.

Preferably, the device 1 does not comprise a flow valve or a

valve for reducing the pressure in the circuit (pressure drop)

between the compression stages, between the expansion stages or

downstream of the expansion of the cycle. Thus only isolating

valves for maintenance purposes may be provided in the cycle

circuit 14.

That is to say that the operating point of the turbines 17

(speed, pressure) can be regulated solely by way of the

dimensional characteristics of the turbine 17 (no throttling

valve at the turbine inlet, for example). This increases the

reliability of the device (no potential problem involving

failure of valves for controlling the process, since they are

absent). This furthermore makes it possible to eliminate

expensive ancillary circuits (safety valves, etc.) and

simplifies manufacture (reduction in the number of lines to

isolate, etc.).

The use of a helium-based cycle gas makes it possible to reach

temperatures with a view to supercooling liquefied hydrogen

without the risk of a subatmospheric zone within the process

(this would be dangerous if the cycle fluid were hydrogen) and

without the risk of freezing of the cold source (the maximum

liquefaction temperature of helium is equal to 5.17 K). The

effect of supercooling liquefied hydrogen has a very notable

advantage for the transport chain of the hydrogen molecule and

then potentially for users (typically liquid stations) by virtue

of the reduction in boil-off gases during haulage.

It is thus possible to reach the freezing point (13 K) of the

flow of hydrogen to be liquefied without crystallizing the cold

source.

The low-pressure portion of the cycle circuit 14 may be operated

at a relatively high pressure. This makes it possible to reduce

the volumetric flow rates in the heat exchangers 6, 7, 8, 9, 10,

11, 12, 13. The working pressure of the cycle gas can thus be

decorrelated from the pressure or the target temperature of the

fluid to be cooled. This pressure of the cycle gas can thus be

increased to adapt to the constraints of the turbomachine but

also to reduce the volumetric flow rate at low pressure, which

is generally one of the major parameters determining the

dimensions of the heat exchangers.

This low pressure level in the cycle circuit 14 is for example

greater than or equal to 10 bar and can typically lie between 10

and 40 bar. This reduces the volumetric flow rate in the heat

exchangers, which counterbalances the low compression rate per

compression stage.

As illustrated, the device 1 may comprise a second cooling system

in heat exchange with at least part of the set of heat

exchanger(s) 5 in heat exchange with the cycle gas, for example.

This second cooling system 21 comprises, for example, a circuit

25 for heat transfer fluid such as liquid nitrogen or a mixture

of refrigerants which cools the cycle gas and/or the hydrogen to

be liquefied by means of the first countercurrent heat exchanger

or the first countercurrent heat exchangers, and may also make

it possible to combat losses by difference at the hot end caused

by circulating the heat transfer fluid or fluids in a closed

loop, as illustrated in [fig. 1] via at least one pre-cooling

exchanger 5.

This second cooling system 21 makes it possible, for example, to

pre-cool the fluid to be liquefied and/or the working gas at the

outlet of the compression mechanism. This refrigerant

circulating in the circuit 25 for heat transfer fluid (for

example in a loop) is for example provided by a unit 27 for

producing and/or storing 28 this refrigerant. If appropriate,

the circuit 3 for fluid to be cooled passes through via this unit 27 in order to be pre-cooled upstream. It should be noted that it is conceivable for the device 1 to have other additional cooling system(s). For example, a third cooling circuit supplied by a chiller (for example providing a cold source at a temperature typically lying between 50C and -60°C) may be provided in addition to the aforementioned system. A fourth cooling system could also be provided to again provide cold to the device 1 and increase the liquefaction power of the device

1 if required. The embodiment of [fig. 2] is distinguished from

the preceding one solely in that the cycle circuit 14 comprises

a return pipe 22 having a first end connected to the outlet of

one of the turbines 17 (other than the last one downstream) and

a second end connected to the inlet of one of the compressors 15

other than the first compressor 15 (upstream). This return pipe

22 makes it possible to return part of the flow of cycle gas to

the compression mechanism at an intermediate pressure level

between the low pressure at the inlet of the compression

mechanism and the high pressure at the outlet of the compression

mechanism.

The return pipe 22 may be in heat exchange with at least part of

the countercurrent heat exchangers. A plurality of return pipes

to the compression station at intermediate pressure may

advantageously be installed depending on the desired level of

optimization of the process. For example, the draw-off points

(at the turbines under consideration) and injection points (at

the compression stages under consideration) may be situated at

different pressure levels.

The embodiment of [fig. 3] is distinguished from the preceding

one solely in that the cycle circuit 14 further comprises a

partial bypass pipe 24 having a first end connected upstream of

a turbine 17 (for example the first upstream turbine 17) and a

second end connected to the inlet of another turbine 17 situated

downstream (for example the third turbine). For example, the

bypass pipe 24 makes it possible to divert part of the flow of cycle gas exiting the compression mechanism at high pressure to the coldest turbines further downstream. The rest of the flow passes through this hotter first upstream turbine 17. This makes it possible, depending on the positioning in terms of specific speed of the various turbines and compressors, to adjust the flow rates sent to the various stages. For example, the compressors situated at higher pressure intake a lower volumetric flow rate than the first compression stages (situated close to the low pressure of the process). One way of increasing this volumetric flow rate and thus of potentially increasing their isentropic efficiency is to incorporate a return at intermediate pressure from the expansion stages, as shown in figure 3.

The device 1 shown in [fig. 4] illustrates yet another non

limiting embodiment. The elements that are identical to those

described above are denoted by the same numerical references and

are not described in detail again.

The cycle circuit 14 of the device of [fig. 4] comprises three

compressors (driven respectively by three motors 18). As

illustrated, each compressor may comprise four compression

stages 15 (that is to say four compression wheels in series).

These compressor wheels 15 may be mounted by direct coupling to

one end of a shaft 19 of the motor 18 in question. In this

example, the device therefore has twelve centrifugal compression

stages in series. As shown, cooling 26 of the cycle gas may be

provided every two compression stages.

In this example, the device 1 has five expansion stages in series

(six centripetal turbine wheels, two of which are disposed in

parallel), for example one or two expansion stages per

compressor. As illustrated, all of the turbines 17 may be coupled

to a compressor shaft 19 (for example two turbines 17 are mounted

at the other end of the shaft 19 of each motor 18 to provide the

mechanical work to the compressor wheels 15 that are also mounted

on this shaft 19). Of course, the turbines 17 could be on the same side of the shaft 19 as the compression wheels 15. For example, the four first expansion stages are formed of four turbines 17 in series. The fifth expansion stage is for example formed of two turbines 17 disposed respectively in two branches in parallel of the cycle circuit 14.

The device 1 shown in [fig. 5] is distinguished from that of

[fig. 4] in that it comprises return lines 122, 123, 124 for

cycle gas that transfer part of the cycle gas exiting the

turbines 17 at intermediate pressure levels (medium pressure)

within the compression mechanism. For example, a line 124

connects the outlet of the first turbine to the outlet of the

eighth compression stage. Equally, a line 123 connects the outlet

of the second turbine to the outlet of the sixth compression

stage. Equally, a line 122 connects the outlet of the third

turbine 17 to the outlet of the fourth compression stage. Of

course, the device could have just one or just two of these

medium-pressure return lines. Equally, other return lines could

be envisioned. In addition, the ends of these lines could be

changed (outlet of other turbine(s) and outlet(s) of other

compression stages).

This or these returns make it possible to increase the volumetric

flow rate of the compressors thus supplied with a flow rate

excess and thus to potentially increase their isentropic

efficiency.

The device 1 shown in [fig. 6] illustrates a detail of the device

1 illustrating a non-limiting possible example of the structure

and operation of a motor-turbocompressor arrangement. One end of

the shaft 19 of the motor 18 drives four compressor wheels (four

compression stages 15). The other end of the shaft 19 is coupled

directly to two expansion stages (two turbines 17).

Of course, any other suitable type of arrangement of the

compression stages 15 and expansion stage 17 (number and

distribution) may be envisioned (likewise for the number of

motors).

Thus other modifications are possible.

Various configurations are therefore possible for the turbines

17, notably for the downstream turbines (the coldest ones).

For example, as already illustrated, the two last expansion

stages (two turbines) may be installed in parallel and not in

series. This makes it possible to effect a greater enthalpy drop

across these turbines. This would be realized to the detriment

of the efficiency (since two turbines would share 100% of the

flow rate and the available pressure difference would be almost

doubled). In spite of this potential drop in efficiency for these

two last expansion stages, realizing a greater enthalpy drop

could allow the expansion to be staged more effectively.

This is because the same enthalpy differential in cold conditions

causes a variation in temperature across a turbine that is

smaller than in the case of a hotter turbine. This improves the

efficiency of the refrigeration and liquefaction process. Thus,

in spite of a relatively reduced temperature differential across

the turbines, the efficiency of the device makes it possible to

liquefy hydrogen with good energy efficiency.

The temperature differential caused by the turbine 17 may be a

function of the temperature of the cycle gas upstream of the

turbine 17.

A buffer tank (not shown) and a set of valve (s) may be provided,

preferably at the low pressure level, with the aim of limiting

the maximum pressure for filling the cooling circuit with gas.

Preferably, the minimum compression rate lies between 1.3 and

1.6 across the compression station. The cycle gas may be composed

100% or 99% of helium and supplemented by hydrogen, for example.

The cycle circuit may comprise, at the inlet of at least one of

the turbines 17, an inlet guide vane ("IGV") configured to

regulate the flow rate of fluid to a determined operating point.

In addition, the arrangement of the compressor wheels 15 and/or

turbines 17 is not limited to the examples above. Thus, the

number and arrangement of the compressors 15 may be modified.

For example, the compression mechanism could be composed of only

three compressors, each compressor could be provided with a

plurality of compression stages, for example three compression

stages, that is to say three compressor wheels (with or without

inter-stage cooling).

[Fig. 8] illustrates another example with two compression stages

(wheels) in series and one expansion stage (wheel).

Equally, two compression stages 15 could be disposed in parallel

and in series with other compression stages (for example three

in series). The two compression stages in parallel can be placed

upstream of the others and thus provide, in the downstream

direction, a relatively high flow rate at the low pressure by

using machines which may all be identical.

In the same way, turbines 17 can be placed in parallel in the

cycle circuit 14.

In addition, as already illustrated, all of the turbines could

be coupled to one or more compressor wheels (for example one or

more turbines 17 coupled to the same shaft 19 as one or more

compression stages).

As illustrated, the circuit 3 for fluid to be cooled may comprise

one or more catalysis members (converter(s) 280) outside of

exchangers or section(s) 29 of exchanger(s), for example for

(ortho-para) hydrogen conversion.

Claims (3)

1. A device for refrigerating and/or liquefying a fluid such

as hydrogen and/or helium, comprising a circuit (3) for fluid to

be cooled having an upstream end intended to be connected to a

source (2) of fluid and a downstream end (23) intended to be

connected to a member (4) for collecting the fluid, the device

(1) comprising a set of heat exchanger(s) (6, 7, 8, 9, 10, 11,

12, 13) in heat exchange with the circuit (3) for fluid to be

cooled, the device (1) comprising at least a first cooling system

(20) in heat exchange with at least part of the set of heat

exchanger(s) (6, 7, 8, 9, 10, 11, 12, 13), the first cooling

system (20) being a refrigerator that performs a refrigeration

cycle on a cycle gas, said refrigerator (20) comprising the

following, disposed in series in a cycle circuit (14): a

mechanism (15) for compressing the cycle gas, at least one member

(16, 5, 6, 8, 10, 12) for cooling the cycle gas, a mechanism

(17) for expanding the cycle gas and at least one member (13,

12, 11, 10, 9, 8, 7, 6, 5) for heating the expanded cycle gas,

wherein the compression mechanism comprises a plurality of

compression stages (15) in series that are composed of a set of

centrifugal impeller compressor(s) (15), the compression stages

(15) being mounted on shafts (19, 190) that are driven in

rotation by a set of motor(s) (18), the expansion mechanism

comprising at least one expansion stage composed of a set of

centripetal turbine(s) (17) having a determined working pressure

at the inlet, and wherein the turbine (17), or respectively at

least one of the turbines (17), is coupled to the same shaft

(19) as at least one compression stage (15) so as to provide the

mechanical work produced during the expansion to the compression

stage (15), characterized in that the at least one turbine (17)

and the corresponding compression stage that are coupled are

structurally configured such that the pressure of the cycle gas

exiting the turbine (17) differs by no more than 40% and

preferably by no more than 30% or by no more than 20% from the pressure of the cycle gas at the inlet of the compression stage

(15), and in that the at least one turbine (17) and the

corresponding compression stage that are coupled are

structurally configured such that the pressure of the cycle gas

entering the turbine (17) differs by no more than 40% and

preferably by no more than 30% or by no more than 20% from the

pressure of the cycle gas at the outlet of the compression stage

(15), and in that the expansion rate across the at least one

turbine (17) coupled to a compression stage is configured to

produce a drop in pressure of the cycle gas, the value of which

differs by no more than 40% from the value of the increase in

pressure across the compression stage (15) to which said turbine

is coupled.

2. The device as claimed in claim 1, characterized in that the

expansion mechanism comprises at least two expansion stages in

series that are composed of a set of centripetal turbines in

series, and in that, in the direction of circulation of the cycle

gas, at least two turbines (17) in series are coupled

respectively to compression stages (15) considered in the

reverse order of their disposition in series, that is to say

that at least one turbine (17) is coupled to a compression stage

(15) situated upstream of a compression stage (15) coupled to

another turbine (17) which precedes it in the cycle circuit (14)

3. The device as claimed in either one of claims 1 and 2,

characterized in that the compression mechanism comprises solely

centrifugal compressors (15).

4. The device as claimed in any one of claims 1 to 3,

characterized in that the expansion mechanism comprises solely

centripetal turbines.

5. The device as claimed in any one of claims 1 to 4,

characterized in that it comprises n turbines and k compressors, n and k being integers such that k is greater than or equal to n.

6. The device as claimed in any one of claims 1 to 5,

characterized in that the mechanical coupling of the at least

one turbine (17) and of the compression stage or stages (15) to

one and the same shaft (19) is configured to ensure an identical

or substantially identical rotational speed of the turbine (17)

and of the compression stages (15) that are coupled.

7. The device as claimed in any one of claims 1 to 6,

characterized in that it comprises sixteen compression stages

(15) and eight turbines (17), or twelve compression stages (15)

and six turbines (17), or eight compression stages (15) and four

turbines (17), or six compression stages (15) and three turbines

(17), or four compression stages (15) and three turbines (17),

or three compression stages and two or three turbines, or two

compression stages and one or two turbines.

8. The device as claimed in any one of claims 1 to 7,

characterized in that the set of heat exchanger(s) comprises at

least one heat exchanger (5, 6, 7, 8, 9, 10, 11, 12, 13) in which

two separate portions of the cycle circuit (14) under separate

thermodynamic conditions perform circulation simultaneously in

countercurrent operation for the cooling and the heating of the

cycle gas, respectively.

9. The device as claimed in any one of claims 1 to 8,

characterized in that it comprises a second cooling system in

heat exchange with at least part of the set of heat exchanger(s)

(5, 6, 7, 8, 9, 10, 11, 12, 13), said second cooling system (21)

comprising a circuit (25) for heat transfer fluid such as liquid

nitrogen or a mixture of refrigerants.

10. A process for producing hydrogen at cryogenic temperature,

notably liquefied hydrogen, using a device (1) as claimed in any one of the preceding claims, wherein the pressure of the cycle gas at the inlet of the mechanism (15) for compressing the cycle gas lies between two and forty bar abs and notably lies between eight and thirty five bar abs.

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 1/7 1/7

[Fig. 1]

15 19 18 15 18 18 190 18

2 16 19 190

16

27

21 25 28 5 3 6 280 14

19

7 20

17

8 280

1 9 19

10

11

12 29 17

13 19

23

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 2/7 2/7

[Fig. 2]

15 19 18 15 18 190 18 18

2 16 19 190 16

27 21 25 28 5 3 6 280 14 22 19

7 20

17

8 280

1 9 19

10

11

12 17 29

13 19

23

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 3/7 3/7

[Fig. 3]

15 19 18 15 18 18 190 18

2 16 19 190 16

27

21 25 28 5 3 6 280 14 22 19

7 20 17

8 280

1 9 19

10

11

12 17 29

13 19

23

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 4/7 4/7

[Fig. 4]

26 : 26 26 26 26 15 262 I 15

15 15 15 15

2

19 5

M 18 14 27 3 19

21 19 25 28 6 280 18 7 M 17 8 19 9

10

11

12 XX 17 29 13 19

29 18 M 19

17

23 4

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 5/7 5/7

[Fig. 5]

26 26 26 26 26 2 15 26, 15

15 15 15 15 122 123

2 124

19 5 M 18 3 27 14 19.

21 19 25 28 6 -280 18 7 M 17 8 19 9

10

x 11

12 17 EX 29 13 19

29 18 M 19

17

29

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 6/7 6/7

[Fig. 6]

17

19

17

18

19

15

15

[Fig. 7]

15 19 17 2t

P1c Pqt P2c

WO 2022/171485 WO 2022/171485 PCT/EP2022/052295 PCT/EP2022/052295 7/7 7/7

[Fig. 8]

18 19 15 15 18 190

6

3 17